Crossover protection system for railroads



Jan, 10, 1950 s. w. FREEMAN CROSSOVER'PROTECTION SYSTEM FOR RAILROADS Filed April 12, 1945' attorney Patented Jan. 10, 1950 CROSSOVER PROTECTION SYSTEM FOR RAILROADS Sydney W. Freeman, White Plains, Ni Y., assignor to General Railway Signal Company, Rochester, N. Y.

Application April 12, 1945, Serial No. 587,937

7 Claims.

This invention relates to a crossover protection system and more particularly to such a system in which a light beam is employed to detect the presence of a car or a train on a crossover or other track section.

By reason of the number of insulating joints required and the short rail sections therebetween it is sometimes dificult to provide track circuit protection on a crossover.

In View of the foregoing it is proposed, in accordance with the present invention, to transmit a light beam substantially parallel to and substantially midway between the track rails of the crossover at train coupler height so that the presence of a car on the crossover will intercept the light beam and thereby prevent the transmission of light over the path of the proposed light. beam; to provide a photoelectric cell, phototube or other suitable light responsive means to detest the transmitted light; to provide, whereby necessary, an amplifier to amplify the electrical energy delivered by the photoelectric cell or tube and to provide suitable electro-responsive or sig-' nal means. controlled by the amplifier to restrict, the movement of other trains.

In order to prevent the manifestation of an unoccupied crossover due to some other source oi light, such as day light, it is further proposed tointerrupt or fluctuate the light beam at a predetermined rate and to provide suitable tuned means or decoding means which will respond only if energy is applied thereto at a predetermined rate.

As another object of the presentinvention it is proposed to employ a stick relay for manifesting, when energized, an unoccupied condition of the crossover which relay is normally held up through a stick circuit which is interrupted each. time that the crossover is used, and to transmit the interrupted light beam and render the amplifier operative only when this crossing detection stick relay is in a deenergized condition and the crossover switches are set for the main. track.

Other objects, purposes and characteristic features of the invention. will in: part be pointed out hereinafter and will in part be obvious from the: accompanying drawing showing one embodiment of the present invention.

Structure.-Referring,to the drawings it will be observed that there has been illustratedan: eastbound track consisting of rails I t divided into sections byinsu-latingjoints H" at the. approach tothe crossover to which is provided a signal SI: controlled by trafllc conditions in advance by means including the track relay Tl There is also illustrated a westbound track consistingof track rails I2 divided into block sections by insulating: joints l3 and which: is provided at the approach to the crossover with a signal S2 con-- trolled in accordance with traflic: conditions in advance by means including the track relay T2. The crossover includes a track switch SWI' as.- sociated with track rails l0 and. the track switch SW2 associated with track rails 12. The crossover is also provided with insulating; joints; i5 and ["6 to properly insulate. the rails of the main, tracks from each other and to insulate the eastbound and westbound railroad tracks from each other for all positions, of the track switches SW l and SW2.

As illustrated there is provided a light pro,- jecting unit LPU located at. coupler height abovethe track rails including a suitable visible light or ultra violet wave energy creating means: which may be assumed to be a concentrated filament incandescent lamp 20,, a light concentrating lens? 21 for directing the light emitted by lamp 20- and in part reflected by reflector 22 into a comparatively narrow beam illustrated by a dotted line 23. A spherical reflector 22 is preferably used so that the light from the filament reflected by the reflector will pass: near the filament and the focus of the lens 2|. In the path of this; light beam 23 there is provided, preferably also at coupler height, a light detecting unit LDU including a photoelectric cell or phototube 25, upon which the lightvbeam 23 is concentrated through the medium of a lens 26". In the particular embodiment illustrated this tube 25 is assumed to be a phototube. Both the light projecting" unit LPU and the light detecting unit LDU are preferably provided with comparatively long tubular shields 28 and 29 respectively, for the pur-- pose of keeping day light or other extraneous light from the reflector 22; and the photoelectric" cell 25 respectively;

Asshown the lamp 21! is energized through the mediumof the front contact 30 of the code'creat-' ing relay CT; whereas the grid 0 of suitable amplifying means, conventionally illustrated by the amplifying tube A, is connected to. the out-put terminal of the phototube 2- 5 through the medium of condenser Cl, a suitable leakage resistance 3?; being provided to prevent a charge being retained too long on the grid of this amplifier A. More specifically this phototube 25- comprises a cup-shaped cathode 25- ball-shaped anode. 252 included in series with: battery LB; and resistance. unit 3.6. The ohmic: resistance of unit 361s preferably quite high so that a substantial voltage drop will exist thereover when a small amount of current from battery LB fiows therethrough due to light striking the cathode The heater h of the amplifier A and the coding relay CT both receive their energy from a heater battery HB through a circuit which may be traced from the (-1-) terminal of this battery HB through back contact 33 of the crossing stick relay XS, switch box contact CIA, closed only when the track switch SW1 is in the main track position, switch box contact C'ZA closed only when the track switch SW2 is in the main track position, the heater h, and in multiple therewith the back contact 34 of the coding relay CT in series with the winding of this coding relay. It is readily seen that application of energy to this circuit will cause heating of the cathode. It will also cause the coding relay CT to intermittently interrupt its energizing circuit by the opening of this back contact 34 to thereby cause intermittent closure of its front contact for energizing the lamp 22. This operation is known as door-bell action and if desired the moving parts of the relay CT may be mechanically tuned to a predetermined frequency. That is the relay may be of the type as shown in the patent to Field No. 2,351,588, dated June 20, 1944. The plate circuit for the amplifier A may be traced from the terminal of the plate battery PB through the primary winding of the transformer Trl, the plate p of the amplifier A, the cathode Ca of the amplifier A back to the minus terminal of the plate battery PB. The secondary winding of this transformer TM is connected to the code following relay CFR. This code following relay CFR is provided with a contact 35 which contact when in its attracted position applies energy from the terminal of of a suitable source of current to one end of a primary windin of a transformer Tr2 and when its retracted position connects this same terminal of'the source to the other extreme end of such primary winding, the mid-point of which Winding is connected to the terminal of the same source. This construction will cause .f.

alternating magnetism to be set up in the core of the transformer TTZ in step with the intermittent operation of the contact 35. The secondary winding of this transformer T12 is connected to the primary windin of a transformer T13 through a circuit including condenser C2 of a capacity such as to tune th circuit in which it is included to the same coding rate as that of the code created by the code transmitting relay CT. The secondary winding of the transformer Trt is connected to the input terminals of a full-wave rectifier R the output terminals of which are connected to the decoding rela or receiving relay REC. The relay REC is provided with a front contact 38 included in the pick-up circuit for the crossin detecting stick relay XS. It will be observed that a similar pick-up circuit includin the manually operable push button PBX is provided and that a stick circuit includ ing the stick contact 43 is provided for this crossing detecting stick relay XS. Each of these pick up and stick circuits includes switch box contacts CIB and 02B. In other words, the relay XS may be picked up by momentary closure of contact 38 or by momentary depression of push button PBX and may then be held energized by a stick-pin cuit including its own stick contact 45 and each of these functions requires that the switch box contacts CB and CZB be closed.

Operation.-The apparatus illustrated in the drawing is shown in its normal condition and it should be observed that the coding relay CT and the heater h of the amplifier A are normally deenergized and that with the heater it once cooled the plate-to-anode portion of the plate circuit including the plate battery PB is of such high resistance that substantially no current flows in this plate circuit and that the lamp 2!] is also normally deenergized.

Let us now assume that a train is to be backed from the eastbound track ill into the westbound track l2 over the cross-over SWl-SW2. Both of the track switches SWi and SW2 will first be operated to their abnormal position as through the medium of switch stands or switch machines (not shown). This will of course cause opening of the switch box contacts C'lA, ClB, CZA and 02B. The opening of contacts 0113 or C'lB will of course cause dcenergization of the crossin detecting stick relay XS because contact 38 is still open, thereby resultin in the opening of con-- tacts 4i and 42 included in the proceed circuits for signals Si and S2 respectively. Both of the signals Si and S2 will of course be operated to their stop position and will in turn by means not shown cause the next ignal in the rear thereof to be operated to the caution position. It should be understood that suitable provision is preferably made (not shown) so that the track switches SWI and SW2 cannot be operated from their main track position if there is a train approaching such track switch at speed.

Let us now assume that the train moves over the crossover SWISW2 and that these switches SWl and SW2 are thereafter returned to their normal main-track position. The return of these switches SW! and SW2 to their normal position recloses the switch box contacts CIA, C'lB, 02A and 02B. Since the back contact 33 of the stick relay XS is now closed the coding relay CT will be intermittently picked up by door-bell action to create a code of a predetermined rate dependent upon the design and mechanical tuning of this relay CT. Other methods for producing coded current may obviously be used. This coding may for instance be a rate code having a suflicient number of impulses per minute so as to distinguish it from extraneous flashing light in that neighborhood. The intermittent closure of the contact 39 of the relay CT will cause intermittent energization of the lamp 28 to thereby create a coded light beam conventionally shown by dotted line 23. If a car has not been accidentally left on the crossover SWI-SW2 the photoelectric cell 25 will be rendered active intermittently at this coding rate, by reason of the intermittent variation in current flowing in resistance unit 36, to thereby cause intermittent application of energy through condenser CI to the grid 9 of the amplifier A. Presumably the cathode Ca has been heated to a sufficient extent by the heater it that this intermittent application of voltage to the grid g of the amplifier A will cause intermittent flow of current in the plate circuit'of this amplifier and including the primary Winding of the transformer T1]. The grid 9 is preferably biased, as by battery 31 and potentiometer 39 so as to cause the amplifier A to operate as either a class B or a classC amplifier; The flow of such current in the plate circuit will cause intermittent picking up of the code following former T12 to in turn generate alternating our rent attheccding rate in the secondary winding of this trans-former If the relay a neutral relay the rectifier RE is preferably in-i cluded in series therein or else the transformer T11 is omitted since the pulses of direct current can then intermittently pick up this relay. If the transformer Trl retained and the rectifier R! is omitted the code following relay CFR. is preferably a two-position polar relay; so that it: Will'be operated in opposite directions by the two halves of each. cycleof the alternating current delivered by this transformer TrL'. 'Since the: secondary winding of the transformer T1? is tuned to this coding rate by the condenser C2 and will: not allow the flow of current of a firequency appreciably different from that of the coding rate frequencythe transformer T'r3- be en ectively energized only if the coding following relay GER is operated at: the coding rate for which the codingrelay CT has been adjusted.

The output energy flowing from the secondary winding. of the transformer T73. is then rectified through the medium of the full-wave rectifier R; and causes substantially continuous energization of the decoding relay so that this relay REC maintains its contact so continuously closed inspite of the intermittentoperation of the contact 35; of the decoding relay CFR. The picking up of the decoding relay REC will; by the closure of its front contact 38, complete a; pick-mp circuit for the crossing detecting stick relay XS which may be readily traced: in. the drawing, and since the switch box contacts C1 3 and 62B have been reclosed this relay XSI will be maintained energized through the; medium of its stick circuit-including stick contact 39:. The picking up of the relay XS, which will remain stuck'up so long asthe crossing is not used, will of course reclose the signal. circuits at contacts M and; 42 and will remove energy: at its back contact 33 from the coding relay CT and the heater h, of the amplifier A. With the coding relay- CT permanentlydeenergized the lamp Z6 is also permanentl y deenergized, that is, at iea-st until the crossover is: again used. The tubular shield or sun shades 28 and 29: are provided to: keep sun lightand other extraneous light such as light from headlights out of the casings of the light projecting unit LPU and light detecting unit l-hese tubes, preferably have their insides blackened so: as; to absorb, and not reflect, such foreign light, as. enters these shields. In order to further" assure against improp r peration oi the system the phototubeZEtis prcferabl operated at such a point in its. operating characteristic that. the light responsive current, cannot reach its nraxin'nlm'"valuev due to foreign light entering the light detecting unit LDU so that the tube will function to follow the code in spite of such effect as continuous foreign light entering the light detecting unit LDU may cause. In other words, any foreign light that enters the light detecting unit LDU will be either continuous in nature or if varying will at least not vary at the prescribed code for which the decoding apparatus including the condenser C2 is tuned. In other words, even though foreign light may cause a certain amount of light responsive current to flow this current cannot result in the picking up of the decoding relay REC and furthermore the phototube will not reach its saturation point due to such current and therefore the amplifier will follow the pulsating voltages applied to the grid 9 thereof through condenser CI due to the action of the intermittent light; beam The push. button is preferably scaled or locked and is. under instruction to beonly after the cross-over has been thoroughly' checked for occupancy and. is provided; to permit clearing of the! signals. Si and S2 in the, event the detecting means: is. outof order.

. Having thus shown and described one: specific embodimentof the present. invention it should be; understood thatthe. particular embodiment illustrated: has. been selected" to. facilitate description or the principle. or operation. of the system contcmplated; and. the functions. which this system is. intended to: perform, and it should be understood. that various other forms of the invention maybe used; and various changes, modifications.

additionsmay be made to. adapt the invention to. the. particular problem encountered in. practicing the same without departing from the spirit .or scope: of; the invention except as (13,

. mandedby thescope of the following claims.

What claim as new is:

1. Car detecting means for crossovers com, prising, a crossover track. including two track switches, a first set: or contacts closed only when said track switches assume their main track positions; a. second set of contacts closed only when s'aidi track switches assume. their maintrack positions,.a stickrelay, light. beam creating means for transmitting a, light. beam intermittently across. such. crossover substantially parallel to the track rails: andsubstantiallyrmidway between the track rails or.- said crossover; means; for detecting; said light beam. and, converting it into intermittent impulses; of, electric current, amplifying; means ior'amrliiying said current, decoding mcanscontrolled by current derivedfrom said amplifying means and responsive only if said intermittent current of predetermined frequency, a pick-up. circuit for said stick relay including a contact closed only if:v said decoding means is active, a. stick circuit for-said stick rela-y including its: own holding contact and. said first set of contacts, and means; for rendering said light creating means; active including said second" set of contacts and. a back contact of said stickrelay in series.

'ZaCar' detecting, means for crossovers comprising; a crossover track. including two track switches-pa first set of contacts; closed only when: said track: switches assume their main track positions,. a second. set. of contacts closed, only whensaidtraclr switches; assume their-main track positions at. stickrelay; li ht beam creating means. ior transmitting. a light beam intermittently acrosssuch crossover substantially parallel to the trackzrails and substantially midway between the track rails: of said crossover-,, means for detectingsaidllight-beam and converting it into in-. termittent impulses of electric current, amplifying means for amplifying said current and. in-- eluding a heater, decoding means controlled by current: derived from said amplifying means and responsive only if said intermittent current is of predetermined frequency, a pick-up circuit for said stick relay including a contact closed only if said decoding means is active, a stick circuit for said stick relay including its own holding contact and said first set of contacts, and means for rendering said light creating means and said heater active including said second set of contacts and a back contact of said stick relay in series.

3. Car detecting means for crossovers comprising, a crossover track including two track switches, a. first set of contacts closed only when spouse said track switches assume their main track position, a second set of contacts closed only when said track switches assume their main track position, a stick relay, light beam creating means for transmitting a light beam intermittently across such crossover substantially parallel to the track rails and substantially midway between the track rails of said crossover, means for detecting said light beam and converting it into intermittent impulses of electric current, amplifying means for amplifying said current, decoding means controlled by current derived from said amplifying means and responsive only if said intermittent current is of predetermined frequency, a pick-up circuit for said stick relay including a contact closed only if said decoding means is active, a stick circuit for said stick relay including its own holding contact and said first set of contacts, means for rendering said light creating means active including said second set of contacts and a back contact of said stick relay in series, and a signal controlled by said stick relay.

4. Car detecting means for crossovers comprising, a light unit for transmitting a light beam substantially parallel to and substantially midway between the crossover rails, a signal controlling stick relay, means responsive only to intermittent impulses of light of a predetermined frequency for picking up said stick relay and located in the path of said light beam and beyond the crossover, means for intermittently lighting said light unit only when said stick relay is deenergized and the crossover is in its main track position, and a stick circuit for said stick relay closed only if it assumes its energized position and said crossover assumes its main track position.

5. In a signalling system of the character described for a track layout having a crossover and a signal for governing traific through the track switch at one end of the crossover; light beam transmitting apparatus at one end of the crossover effective when rendered active to transmit a light beam substantially midway between the track rails of the crossover at car coupler height; contacts associated with the track switch at each end of the crossover closed only when that track switch is in its normal position; means responsive to the reception of light associated with the opposite end of said crossover, apparatus controlled by said means and rendered active in response to 1 the reception of said light beam, said apparatus being effective when rendered active to remain active as long as said contacts remain closed irrespective of the reception of said light beam, and said apparatus being efiective when rendered active to render said light beam transmitting apparatus for the opposite end of the crossover inactive; means for clearing said signal only when said apparatus is active and said contacts are closed, and means including said apparatus for rendering said light beam transmitting apparatus active at a time when said signal is at stop.

6. In a signalling system for railroads, the combination with a track layout having a crossover and a signal for governing trafiic through the track switch at one end of the crossover, of light beam transmitting apparatus at one end of the crossover efiective when rendered active to transmit a light beam substantially at car coupler height and midway between the track rails of the crossover, contacts associated with the track switch at each end of the crossover closed only when that track switch is in its normal position, means including said contacts for rendering said light beam transmitting apparatus active only when the track switches of said crossovers are both in their normal positions, light responsive apparatus associated with the opposite end of said crossover, and circuit means controlled by said light responsive apparatus to be rendered active in response to the reception of said light beam to allow the clearing of said signal, said circuit means being eiiective when rendered active to remain active as long as the track switches of said crossover remain in their normal positions irrespective of the reception of said light beam.

7. In a signalling system for railroads for a track layout having a crossover and a signal for governing trafiic through the track switch at one end of the crossover, contacts associated with each end of said crossover, said contacts being closed only when the track switch at that end of the crossover is in its normal position, light transmitting means at one end of the crossover for transmitting a beam of light directed substantially midway between the track rails and at car coupler height, said light transmitting means being rendered effective upon the closure of said contacts when the track switches of the crossover are restored to their normal positions, means responsive to the reception of light at the opposite end of said crossover actuated in response to said light transmitting means, and means for allowing said signal to clear upon the restoration of the track switches of said crossover to their normal positions only if said light responsive means is actuated to indicate that the crossover is unoccupied.

- SYDNEY W. FREEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 923,170 Hawkins June 1, 1909 1,791,938 Schroeter et al Feb, 10, 1931 2,089,835 Logan, Jr. Aug. 10, 1937 FOREIGN PATENTS Number Country Date 468,350 Germany May 2'7, 1926 501,483 Germany Nov. 30, 1928 

